石羊河流域多水体酸根离子特征及影响因素

2014年7月~2015年6月在石羊河流域采集降水、地表水及地下水样品,使用离子色谱仪分析获取样品主要酸根离子含量,研究石羊河流域不同水体酸根离子特征、季节分异及其影响因素.结果显示：石羊河流域不同水体均呈弱碱性,酸根离子组成以SO₄^2-和HCO₃^-为优势离子,分别占酸根离子总量的38.68%和33.49%;不同季节水体酸根离子浓度差别较大,春季水体中酸根离子浓度最高,夏季最低,地下水季节变异小于地表水;地表水和地下水的酸根离子浓度都呈现出从上游到下游递增的规律,地表水酸根离子浓度大大低于地下水.碳酸盐的风化及蒸发岩溶解是酸根离子的主要来源,人类活动对石羊河流域水体已造成轻度污染.     

长江三角洲初冬一次重污染天气成因分析

利用站点气象和PM_2.5资料以及NCEP的全球再分析数据集研究了2015年12月17~28日长江三角洲地区一次重污染天气过程.结果表明：地面弱气压场是此次污染事件发生发展的主要天气背景,而冷空气带来的大风使PM_2.5浓度迅速下降,有效清除了PM_2.5.区域热力因子和动力因子分析发现,此次过程中大气中低层层结稳定、近地面逆温强,有利于PM_2.5和水汽的累积,使其浓度水平升高;对于动力因子来说,较小的通风率和较低的边界层高度不利于污染物扩散,同样使PM_2.5浓度上升.两者相比,热力因子对PM_2.5浓度值的贡献比动力因子大.结合后向轨迹和排放源分布发现,此次污染过程中长江三角洲地区的PM_2.5主要受来自其西北方向的大陆气团（占46%左右）的影响,这些气团途经高污染排放源并把污染物远距离传输至长江三角洲地区.最后利用PSCF和CWT对长江三角洲地区污染物的潜在来源进行了分析,发现PM_2.5的来源主要集中在安徽、河南、山西、山东以及长江三角洲本地,说明此次过程中长江三角洲地区的污染物浓度受到远距离输送和局地过程的共同影响.     

阿拉善沙漠高原降水化学特征与离子来源判别

为查明我国北方沙漠地区降水化学组成及来源,在阿拉善沙漠高原阿右旗气象站采集了2013—2015年的降水样品,测定了降水pH、EC（电导率）及主要离子当量浓度.结果表明:阿拉善沙漠阿右旗气象站降水pH和EC的范围分别为6.66~8.05和35~1 237 μS/cm;Ca2+、SO₄2-、Na+和Cl-为降水中的主要离子,其总和占总离子的85%以上.降水pH、EC和主要离子当量浓度是反映空气质量的基本参数,较高的降水pH反映出当地降水具有明显的碱性特征.与其他地区相比,该地区降水的EC和可溶性离子日均湿沉降通量也较高,且随月份有较大的变化,表明干旱沙漠粉尘对当地降水水化学的贡献较大.根据离子来源相对贡献的计算结果发现,降水中92.8%的SO₄2-和98%的NO₃-来自人为源,98.8%的Ca2+和88.7%的K+为陆地来源,55%的Mg2+为海洋源,24.8%的Na+来自矿物风化,极少部分Cl-为人为源.研究显示:除降水中的NH₄+外,其他主要离子之间的相关性表明各种成因物质在风力作用下同时进入了大气;基于[NH₄+]（NH₄+的当量浓度）与[K+]（K+的当量浓度）相关性分析,降水中的NH₄+来自生物质燃烧、肥料使用、动物粪便等.      

浙北地区PM2.5中多环芳烃特征

为了研究浙北地区PM_2.5中多环芳烃（PAHs）的季节性变化和它们的来源,于2014年11月~2015年11月收集了杭州和宁波2个城市中4个采样点的PM_2.5样品,利用气-质联用仪测定了17种PAHs浓度.结果表明,∑PAHs年平均浓度范围为24.1~51.9ng/m³,平均值为（35.5 ±12.3） ng/m³.2~3环PAHs在PM_2.5中的浓度较低（<1ng/m³）,而4~6环PAHs占总PAHs的77.0%.∑PAHs的浓度与PM_2.5呈相似的季节性变化特征,冬季浓度最高而夏季最低.惹烯作为软木燃烧的示踪物,冬季的浓度是夏季的4倍,表明在冬季软木燃烧的排放和对PM_2.5的贡献都有所增加.除了夏季的2个城区站点,其它季节和站点∑PAHs浓度和PM_2.5呈现一定的正相关性.特征PAHs比值显示,浙北地区气溶胶相关的多环芳烃主要来自燃烧和热解排放,如生物质燃烧和煤燃烧,而交通排放和石油挥发源的影响不大.     

Effect of sulfur source on photocatalytic degradation performance of CdS/MoS2 prepared with one-step hydrothermal synthesis

Cd S/Mo S_2,an extremely efficient photocatalyst,has been extensively used in hydrogen photoproduction and pollutant degradation.Cd S/Mo S_2can be synthesized by a facile one-step hydrothermal process.However,the effect of the sulfur source on the synthesis of Cd S/Mo S_2via one-step hydrothermal methods has seldom been investigated.We report herein a series of one-step hydrothermal preparations of Cd S/Mo S_2using three different sulfur sources:thioacetamide,L-cysteine,and thiourea.The results revealed that the sulfur source strongly affected the crystallization,morphology,elemental composition and ultraviolet(UV)–visible-light-absorption ability of the Cd S/Mo S_2.Among the investigated sulfur sources,thioacetamide provided the highest visible-light absorption ability for Cd S/Mo S_2,with the smallest average particle size and largest surface area,resulting in the highest efficiency in Methylene Blue(MB)degradation.The photocatalytic activity of Cd S/Mo S_2synthesized from the three sulfur sources can be arranged in the following order:thioacetamideL-cysteinethiourea.The reaction rate constants(k)for thioacetamide,L-cysteine,and thiourea were estimated to be 0.0197,0.0140,and 0.0084 min~(-1),respectively.However,thioacetamide may be limited in practical application in terms of its price and toxicity,while L-cysteine is relatively economical,less toxic and exhibited good photocatalytic degradation performance toward MB.     

Characterizing the antibiotic resistance genes in a river catchment: Influence of anthropogenic activities

Previous studies on environmental antibiotics resistance genes(ARGs) have focused on the pollution sources such as wastewater treatment plants, aquaculture and livestock farms,etc. Few of them had addressed this issue in a regional scale such as river catchment. Hence,the occurrence and abundances of 23 ARGs were investigated in surface water samples collected from 38 sites which located from the river source to estuary of the Beijiang River.Among them, 11 ARGs were frequently detected in this region and 5 ARGs(sul I, sul II, tet B,tet C, and tet W) were selected for their distribution pattern analysis. The abundances of the selected ARGs were higher in the upstream(8.70 × 10~6 copies/ng DNA) and downstream areas(3.17 × 10~6 copies/ng DNA) than those in the midstream areas(1.23 × 10~6 copies/ng DNA), which was positively correlated to the population density and number of pollution sources. Pollution sources of ARGs along the Beijiang River not only had a great impact on the abundances and diversity, but also on the distribution of specific ARGs in the water samples. Both sul I and sul II were likely originated from aquaculture farms and animal farms,tet W gene was possibly associated with the mining/metal melting industry and the electric waste disposal and tet C gene was commonly found in the area with multiple pollution sources.However, the abundance of tet B was not particularly related to anthropogenic impacts. These findings highlight the influence of pollution sources and density of population on the distribution and dissemination of ARGs at a regional scale.     

Measurement of minimum ignition energies (MIEs) of dust clouds – History,present, future

Nearly 130 years ago Holtzwart and von Meyer (1891) demonstrated by experiments that explosible dust clouds could be ignited by inductive electric sparks. Then more than half a century passed before the publication of the important quantitative research of Boyle and Llewellyn (1950) and Line et al. (1959). They worked with capacitive electric sparks and found that the minimum capacitor energies ½CU² required for ignition of various dust clouds in air decreased substantially when a large series resistance, in the range 10⁴–10⁷ Ω, was introduced in the discharge circuit. When considering that the net energies of the sparks themselves were only of the order of 10% of the ½CU² discharged, the minimum net spark energies required for ignition with a large series resistance were only a few per cent of the net energies required without such a resistance.Line et al. observed that the essential effect of increasing the series resistance, and hence increasing the discharge time of the sparks, was to reduce the disturbance of the dust cloud by the blast wave from the spark. This phenomenon was explored further by Eckhoff (1970, 2017), and subsequently by some simple experiments by Eckhoff and Enstad (1976). Franke (1974, 1977) and Laar (1980) confirmed the additional finding of Line et al. (1959) that the minimum ½CU² for ignition is also substantially reduced by including a series inductance in the discharge circuit, rather than a series resistance. The basic reason is the same as with a large series resistance, viz. increased spark discharge time and hence decreased disturbance of the dust cloud by blast wave from the spark. For this reason inclusion of an appreciable series inductance in the spark discharge circuit is an essential element in current standard MIE test methods.In experiments with spark ignition of transient dust clouds produced by a blast of air in a closed vessel, it is necessary to synchronize the occurrence of the spark with the formation of the dust cloud. The precision required from this type of synchronization is typically of the order of 10 ms, which can be obtained even by mechanical arrangements, such as rapid change of spark gap length, or of the distance between two capacitor plates. The present paper reviews some methods that have been/are being used for achieving adequate synchronization of dust cloud appearance and spark discharge. Some current standard experimental methods for determining MIEs of dust clouds experimentally have also been reviewed. The same applies to some theories of electric-spark ignition of dust clouds.At the end of paper some suggestions for possible future modifications of current standard methods for measuring MIEs of explosible dust clouds are presented. With regard to justifying significant modifications of existing standard methods, the “bottom line” is, as quite often in many connections, that any modifications should be based on realistic cost/benefit evaluations.     

以可生物降解固体为碳源的城市污水厂尾水反硝化脱氮研究

针对城市污水厂尾水氮排放不达标的现象,提出以可生物降解聚合物作为固体碳源的反硝化生物滤池技术。研究结果表明,尾水中氮的去除率会随水力停留时间(HRT)的延长而增加,HRT≤8 h时,去除率增长速度较快;HRT>8 h时,脱氮效率增长趋于平缓。选用聚羟基丁酸戊酸共聚酯(PHBV)为碳源,HRT为8 h时脱氮效果最佳,连续稳定运行30 d,出水硝态氮的去除率达96.1%~97.4%,出水中总氮浓度达GB 3838—2002《地表水环境质量标准》Ⅴ类水标准。     

固定源飞灰中PCDD/Fs的时间变化特性分析

对河北省某生活垃圾焚烧厂(固定源)飞灰中二恶英(PCDD/Fs)含量随时间的变化特性进行了分析,并结合美国、欧盟和国内排放标准限值和3种常见垃圾(医疗垃圾、生活垃圾和工业危险废弃物)以及PCDDs/PCDFs比值,分析了焚烧飞灰中PCDD/Fs特征。结果表明:2014年10月—2015年11月PCDD/Fs的TEQ变化范围为0.00322~0.671μg I-TEQ/kg,同时O8CDD(5.020%~34.19%)、2,3,7,8-T4CDF(0.764%~9.696%)和1,2,3,7,8-P5CDF(0.273%~8.575%)均在PCDD/Fs浓度中占据主要贡献率,2,3,4,7,8-P5CDF(12.12%~68.53%)在PCDD/Fs毒性当量中占据主要贡献率,并且均低于美国、欧盟和国内排放标准限值,同时发现PCDDs/PCDFs TEQ比值与焚烧垃圾类型存在一定关系;本研究样品中PCDD/Fs的合成机理符合从头反应的理论。     

滇池流域宝象河水库沉积物中多环芳烃的垂直分布特征及来源解析

采用GC-MS检测了滇池宝象河水库沉积物中16种美国环保署(US EPA)优先控制的多环芳烃(PAHs)的含量,并对其垂直分布特征及来源进行分析,以此了解宝象河水库近年来PAHs的变化.结果表明,水库沉积物中16种PAHs均有检出,其含量范围为162.26~762.24ng·g~(-1),平均值为423.30 ng·g~(-1).自底层50 cm至表层,沉积物中PAHs含量呈上升趋势.从多环芳烃环数来看,沉积物中的PAHs以2~3环为主,其含量为128.34~518.81 ng·g~(-1),平均值为279.88 ng·g~(-1),占PAHs总量的42.2%~84.1%,平均值为67.6%.FLA/(FLA+PYR)、Ba A/(Ba A+CHR)和Icd P/(Icd P+Bghi P)3组比值及PAHs各组分的分析结果表明,燃烧过程是沉积物中PAHs的主要来源,主要为煤炭、生物质的燃烧.PAHs含量与总有机碳(TOC)之间有显著正相关关系,TOC影响宝象河水库沉积物中PAHs的分布.